Method and manufacturing low leakage MOSFETs and FinFETs

ABSTRACT

By aligning the primary flat of a wafer with a (100) plane rather than a (110) plane, devices can be formed with primary currents flowing along the (100) plane. In this case, the device will intersect the (111) plane at approximately 54.7 degrees. This intersect angle significantly reduces stress propagation/relief along the (111) direction and consequently reduces defects as well as leakage and parasitic currents. The leakage current reduction is a direct consequence of the change in the dislocation length required to short the source-drain junction. By using this technique the leakage current is reduced by up to two orders of magnitude for an N-channel CMOS device.

FIELD OF THE INVENTION

The present invention relates to the fabrication of integrated circuitsand, more specifically, a method for fabricating field effecttransistors (FETs) wherein source-drain current flows along a (100)crystal plane.

BACKGROUND

Semiconductor integrated circuit chips are constructed as dice onwafers. A typical wafer material is crystalline silicon. Wafers are cutfrom single crystal silicon ingots grown from polysilicon by means of,for example, Czochralski method (CZ) crystal growth. CZ wafers arepreferred for VLSI applications as they can withstand high thermalstresses and are able to offer an internal gettering mechanism that canremove unwanted impurities from device structures on a wafer surface.This also gives the wafer a uniform internal structure based onsilicon's diamond cubic lattice structure. Although the diamond cubiclattice provides strength and rigidity to the wafer, defects in thecrystal lattice, for example, slip dislocations, can adversely affectfabricated circuit electrical properties leading to a reduction in thenumber of good dice per wafer. A schematic representation of the diamondcubic lattice structure of silicon is depicted in FIG. 1A.

The atoms in a crystal lattice structure of a silicon wafer align witheach other to form planes traversing the wafer in multiple directions.Three principal planes, and their respective orientations, (100), (110),and (111), are shown in FIGS. 1B-1D. Equivalent planes are designated bybraces, for example, {111}, {110}, and {100}, represent equivalents tothe (111), (110), and (100) principal planes, respectively. In manyapplications, orienting the crystal to an equivalent plane will achievethe same result as aligning it to its principal plane. Many structuralproperties of silicon depend on its planar orientation. Plane (111) hasthe highest number of atoms per unit of surface area and is said to bepacked very tightly. This high atomic density results in a greaternumber of available charge carriers, which allows for faster currentpropagation. Concurrently, the more tightly a crystal plane is packed,the higher the probability that slip dislocations and other defects willoccur. These defects can cause parasitic currents as well as chargeleaks that can lead to poor performance and device failure.

To help identify crystalline planes, wafers are typically fabricatedwith a notch or flat relative to a selected crystalline plane.Throughout the integrated circuit (IC) manufacturing industry, automatedwafer handling equipment utilize these notches or flats, fabricated inthe wafers, to align the wafer, allowing devices on a wafer to bealigned with a specific crystal plane. A development in the art has beenthe shift to formation of semiconductor devices on a silicon waferwherein the devices are aligned so that source-drain current in thosedevices travel along a {110} plane, usually the (110) plane. Asindicated above, a {110} plane has a more closely packed atomicstructure than a {100} plane, which coincides with a higher chargemobility in devices aligned such that current flows along the (110)plane, as compared to devices aligned such that current flows along the(100) plane. A result of this characteristic of silicon crystals isfaster data throughput where device current is aligned along the (110)plane. Several U.S. patents teach the alignment of devices to a (110)plane, for example, U.S. Pat. No. 5,729,045, to Buynosik, entitled“Field Effect Transistor With Higher Mobility,” discloses a method ofincreasing the performance of an FET by aligning channel current withthe (110) crystal plane of a (100) wafer. However, the Buynosik deviceis inappropriate for contemporary high-density device fabrication sinceany defects present in the crystal lattice can have severe deleteriouseffects on an electronic device. Buynosik teaches neither how toeliminate or deal with the lattice defects.

In fact, an ongoing trend in microelectronics devices is a reduction indevice size. Concurrently, with the scaling down of IC devices, devicecurrent paths are smaller and device currents are decreased. One resultis that crystal defects and unintentional currents are proportionallylarger as IC devices become smaller.

One approach to reducing the problems associated with the defectsdiscussed above is to improve the quality of the wafer itself. Onemethod of improving the wafer is through an epitaxial deposition whereina thin layer of single crystal silicon material is deposited on thesurface of a silicon crystal substrate. These wafers are commonly knownas epi wafers. Experimentation has shown that these types of wafers havehigher yields than standard wafers.

In FIG. 2, a silicon wafer 201 is shown with a single MOSFET deviceincluding a source 205, a drain 207, and a gate 209, wherein asource-drain current channel is aligned to a primary flat 203. Theprimary flat is typically aligned with the (110) plane and the arrow(vector) indicates a [110] direction, which is normal to the (110)plane. Most commercially available epitaxial wafers are manufacturedwith the primary flat aligned with the (110) plane. Traditionally,fabrication equipment aligns a wafer using a primary flat (or notch) asa reference. With a primary flat aligned with a (110) plane, devicesconstructed from these epitaxial wafers have current channels that arealigned along the (110) plane. With larger scale devices, this has notbeen a problem since any defects formed had little influence on deviceperformance and could be ignored. However, with design rules everdecreasing, any defects present in the crystal lattice can start to havesevere deleterious effects on an electronic device.

SUMMARY

By aligning the primary flat (or notch) of, for example, an epi waferwith a (100) plane rather than a (110) plane, devices can be formed withprimary currents flowing along the (100) plane. In this case, the devicewill intersect the (111) plane at approximately 54.7 degrees. Thisintersect angle significantly reduces stress propagation/relief alongthe (111) direction and consequently reduces defects as well as leakageand parasitic currents. Leakage current reduction is a directconsequence of the change in the dislocation length required to shortthe source-drain junction. By using this technique, the leakage currentis reduced by up to two orders of magnitude for an n-channel CMOSdevice.

Defects, such as slip dislocation and gettering points for impurities,are also reduced by employing the techniques presented herein.

One application of an embodiment of the present invention relates to thefabrication of metal-oxide-semiconductor field effect transistors(MOSFETs). MOSFET technology is a dominant electronic device technologyin use today. Performance enhancement between generations of devices isgenerally achieved by reducing an overall size of the device, resultingin an enhancement in device speed. This size reduction is generallyreferred to as device scaling. As MOSFETs are scaled to channel lengthsbelow about 200 nm, conventional MOSFETs suffer from several problems.

An improvement in MOSFET performance and yield has been observed byincorporating the present invention into the MOSFET fabrication process.By aligning the MOSFET channel so that source-drain channel currentflows in the (100) plane, manufacturing related defects and relatedleakage and parasitic currents are reduced. Another application ofvarious embodiments of the present invention is in the fabrication of aspecific type of MOSFET device called a FinFET. A FinFET is a MOSFETwith a raised current channel (fin) that utilizes a gate electrode on atleast three sides of the channel. Aligning the fin with the (100) planeresults in a reduction in capacitance between the gate electrode andFinFET channel and body, and superior electrical isolation between thegate electrode and FinFET channel and body. A further benefit of thisfabrication method utilizing a (100) channel direction is that thecorners of the gate electrode are inherently rounded, reducing localelectric fields and consequently increasing the breakdown voltage andimproving uniformity of an electric field in a gate dielectric.Additionally, the (100) channel direction fabrication method describedherein reduces stress in silicon “corners.” This benefit is especiallypronounced during high temperature processing (e.g., during growth of athermal silicon dioxide gate dielectric). One result of the reduction instress is that, for example, less boron p-type doping atoms diffuse outof corner regions into any adjacent existing oxide or growing oxide.There is thus less segregation of the boron into the silicon dioxide.Silicon corner regions maintain a higher doping concentration and,hence, a higher MOS threshold voltage for formation of a parasiticchannel in the finished device. Reduction or elimination in theformation of the parasitic channel at low MOS gate voltages produces asubstantial reduction in leakage current of the device.

Concepts and techniques discussed herein may be added to variouselectronic devices as a mechanism by which leakage current is reduced. Askilled artisan will recognize that the present invention may beincorporated into other embodiments where parasitic device current,defects, and leakage current reduction is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a schematic of a unit cell for a diamond cubic latticecrystal as known in the prior art.

FIGS. 1B-1D show various crystal plane orientations as known in theprior art.

FIG. 2 shows prior art alignment of a primary flat and deviceorientation on a commercially available epitaxial wafer.

FIG. 3 shows the alignment of a primary flat and device orientation on awafer with a (100) primary flat orientation.

FIGS. 4A-4O show exemplary process steps for one embodiment of thepresent invention.

FIGS. 5A-5I show exemplary process steps for another embodiment of thepresent invention.

FIGS. 6A-6K show an exemplary FinFET device fabricated using variousprocess steps of various embodiments of the present invention.

DETAILED DESCRIPTION

As device dimensions continue to shrink and thermal cycling continues toincrease due to an increase in fabrication steps, defects (e.g.,crystalline, contamination, etc.) have a more significant impact ondevice yield and performance. By aligning the primary flat (or notch)of, for example, an epi wafer with the (100) plane rather than the (110)plane, devices can be formed with traditional fabrication equipmentwherein primary currents flow along the (100) plane rather than the(110) plane. In FIG. 3, an epi wafer 301, is shown with a single MOSFETdevice, including a source 305, a drain 307, and a gate 309 wherein asource-drain current channel is aligned to a primary flat 303. Theprimary flat 303 is aligned with the (100) plane. Fabricating deviceswith a primary current path aligned with the (100) plane reduces defectsin and parallel to primary current paths and consequently reducesleakage and parasitic currents, as well as increases device yields.

An exemplary embodiment utilizing the present invention is an n-channelMOSFET device with source-drain current that flows along the (100)plane. While the (100) plane is referred to throughout, a skilledartisan will recognize that many equivalent planes will result in asimilar advantageous intersect angle with {110}, and {111} planes. AsMOSFET fabrication technology is well known in the art, the descriptionthat follows with reference to FIGS. 4A-4O and FIGS. 5A-5I isaccordingly brief.

With reference to FIG. 4A, a substrate 401 has a dielectric layer 403formed thereon. An active layer 405A is formed over the dielectric layer403. In one specific exemplary embodiment, a combination of thesubstrate 401, the dielectric layer 403, and the active layer 405A is asilicon-on-insulator (SOI) wafer. In this embodiment, the dielectriclayer 403 is a buried oxide layer having a nominal thickness of 500 nmwith a practical range of thicknesses being about 15 nm to 1 μm. Athickness of the SOI active layer is nominally 2 μm with a practicalrange of thicknesses being about 0.3μ to 25 μm.

In another specific exemplary embodiment, the substrate 401 could bevirtually any material capable of withstanding process temperatures andcommon chemicals encountered during semiconductor fabrication processes.Such materials would include quartz reticles or glass or plasticsubstrates (i.e., backplanes) used for flat panel displays. In thisexemplary embodiment, the dielectric layer 403 may not be required. Theactive layer 405A could be a deposited polysilicon layer that isdeposited and then annealed (e.g., by rapid thermal annealing (RTA) orexcimer laser annealing (ELA)) to regain a monocrystalline form.

In another specific exemplary embodiment, the active layer 405A could bea thinned wafer bonded to a suitable substrate. In this embodiment, thebonded wafer is a doped p-type wafer with an epitaxial silicon layerformed thereon, although one skilled in the art will recognize that ann-type doped semiconductor wafer may be used to fabricate a p-typeintegrated circuit. Alternatively, a group III-V or II-VI bondedsemiconductor substrate or an oxygen-implanted silicon (SIMOX) substratemay be used.

Overlying the active layer 405A is a first dielectric layer 407A, asecond dielectric layer 409A, and a first photoresist layer 411A. In aspecific exemplary embodiment, the two dielectric layers 407A, 409A area pad oxide with a 20 nm nominal thickness (having a practical range ofabout 16 nm to 50 nm) and a 120 nm nitride layer (having a practicalrange of about 100 nm to 200 nm), respectively.

In FIG. 4B, the first photoresist layer 411A is patterned to produce anetched first photoresist layer 411B. The etched first photoresist layer411B serves as a mask to etch exposed areas of the underlying activelayer 405A. If the active layer 405A is comprised of silicon, siliconmay be wet-etched, for example, with potassium hydroxide (KOH) ortetra-methyl ammonium hydroxide (TMAH). Dry-etch techniques, such as areactive ion etch (RIE) with a fluorine rich plasma (e.g., SF₆) are alsoknown in the art for etching silicon. Once etched, an etched activelayer 405B is produced having a plurality of etched trenches 413. Theplurality of trenches 413 may be, for example, approximately 500 nm indepth but a useful range may span from 150 nm to 800 nm in depth.

The etched first photoresist layer 411B is then removed (FIG. 4C) and aliner dielectric layer 415 is formed over exposed areas of the etchedactive layer 405B (i.e., sidewalls and bottoms of the plurality ofetched trenches 413). The liner dielectric layer 415 may be, forexample, a thermal oxide grown to approximately 30 nm in thickness. Theliner dielectric layer 415 may also be deposited by techniques known inthe art (e.g., by chemical vapor deposition (CVD) or atomic layerdeposition (ALD)).

In FIG. 4D, a second patterned and etched photoresist layer 417 servesas a mask for an ion implant 419 step. The ion implant 419 step producesa plurality of doped regions 421. As one of skill in the art recognizes,the ion implant 419 step may readily be substituted with a dopantdiffusion step.

A shallow trench isolation (STI) blanket dielectric fill layer 423A isformed (e.g., oxide formed by CVD or high density plasma (HDP) assisteddeposition) so as to cover the etched second dielectric layer 409B (FIG.4E). A precise thickness of additional coverage is not critical buttypically ranges from 50 nm to 300 nm over the etched second dielectriclayer 409B. The dielectric fill layer 423A is then planarized (FIG. 4F)to be roughly coplanar with an uppermost portion of the etched seconddielectric layer 409B. The planarization step may be accomplished by achemical-mechanical planarization (CMP) step using an appropriateabrasive slurry. Based on film thicknesses given various specificexemplary embodiments, supra, a planarized STI dielectric fill 423B maybe approximately 700 nm in thickness. Any remaining portion of theplanarized STI dielectric fill 423B overlying the etched seconddielectric layer 409B may be removed with a selective etchant, leavingan etched planarized STI dielectric fill 423C (FIG. 4G). For example, ifthe planarized STI dielectric fill 423B is comprised of oxide and theetched second dielectric layer 409B is nitride, a chemical etchant suchas hydrofluoric acid (commonly contained in a standard buffered oxideetch (BOE)), or orthophosphoric acid, or alternatively a selective dryetch technique (e.g., reactive-ion-etching (RIE)) will effectivelyremove the oxide while having little effect on the nitride.

The etched second dielectric layer 409B is then removed (FIG. 4H)followed by removal of the etched first dielectric layer 407B (FIG. 4I).Assuming the etched first dielectric layer 407B and the etchedplanarized STI dielectric fill 423C are fabricated of materials havingsimilar etch characteristics, removing the first dielectric layer 407Balso produces a secondarily-etched planarized STI dielectric fill 423D.

With reference to FIG. 4J, a thin (e.g., approximately 20 nm)sacrificial dielectric layer 425 is either grown (e.g., if the materialchosen for the sacrificial layer is silicon dioxide) or deposited onexposed areas of the etched active layer. The sacrificial dielectriclayer 425 serves at least two purposes: (1) to remove contaminants,thereby cleaning exposed active regions; and (2) to act as a screeninglayer for subsequent dopant diffusions or implants (not shown). Afterthe sacrificial dielectric layer 425 is formed, various device specificdopant regions may be added to the etched active layer 405B withadditional photoresist masking steps added as required. For example, adoped channel region for an MOS device could be added at this point inthe process flow. Such techniques are device dependent and are known toone of skill in the art.

The sacrificial dielectric layer 425 is then stripped (FIG. 4K). Thesacrificial dielectric layer 425 may be stripped by various wet etch ordry etch techniques as described herein with reference to other similarfilm layers. If the sacrificial dielectric layer 425 and the STIdielectric fill 423D are formed from a similar material (e.g., both arecomprised of oxide), then stripping the sacrificial dielectric layer 425slightly thins the STI dielectric fill 423D as well, leaving a final STIdielectric 423E as indicated in FIG. 4K.

In FIG. 4L, a gate dielectric 427 is formed (e.g., by thermal oxidationor deposition) over now-cleaned and exposed areas of the etched activelayer 405B. In a specific exemplary embodiment, the gate dielectric 427is approximately 80 Å in thickness, although gate thicknesses from 20Å-300 Å are known in the art.

A semiconductor gate layer 429A (e.g., polysilicon) is deposited (FIG.4M). In a specific exemplary embodiment, the semiconductor gate layer isapproximately 350 nm thick but may range in thickness from 150 nm to 600nm. Functionally, the semiconductor gate layer 429A will serve variouspurposes, depending upon a type of device being fabricated. For example,in a Flash memory device, the semiconductor gate layer 429A could serveas a floating gate. In an MOS transistor, the semiconductor gate layer429A could serve as a control gate.

With reference to FIG. 4N ₁, a third patterned and etched photoresistlayer 431 is formed, allowing etching and formation of an etched gatelayer 429B. A physical width, “w,” of a final transistor fabricated fromsuch a structure is indicated in FIG. 4N ₁. In this arrangement, currentflow in a final transistor form would be normal to the page view.

A magnified area “A” is shown in more detail in FIG. 4N ₂. Where theetched active layer 405B has an orientation on, for example a waferwhere the primary flat (or notch) is in a (100) plane (also referred toas a “C-Flat wafer, see FIG. 3), upper corners (i.e., proximate to STItop corners) of the etched active layer 405B are necessarily roundedduring fabrication. This rounding produces a much more uniform electricfield than the sharp corner produced by the prior art. When the electricfield is more uniform, leakage current is suppressed by as much as twoorders of magnitude between a MOSFET source and drain region.Consequently, leakage of charge into or through the gate dielectric 427is diminished.

In FIG. 4O, a final gate 429C overlays a channel region of a MOStransistor (only a single gate is shown for clarity; a skilled artisanwill recognize that gates may be located over each of the active areasoverlaying the gate dielectric areas 427). The gate 429C is surroundedon either side by source and drain dopant regions. (Note: actual dopedregions are not shown but merely indicated by areas 433 where such dopedregion will occur after subsequent processing. Such subsequent processsteps are well-known to a skilled artisan.)

In another exemplary embodiment of the present invention and withreference to FIGS. 5A through 5I, additional and alternative fabricationtechniques are depicted. Similar feature types defined in FIGS. 5Athrough 5I share similar range thicknesses as discussed with referenceto FIGS. 4A through 4O, supra. A skilled artisan will also recognizethat process steps may be intermixed between fabrication steps outlinedbetween the various sets of figures.

In FIG. 5A, a substrate 500 has a dielectric layer 501 formed thereon.In a specific exemplary embodiment, the substrate 500 is a doped p-typewafer with an epitaxial silicon layer formed thereon, although oneskilled in the art will recognize that an n-type doped semiconductorwafer may be used to fabricate a p-type integrated circuit.Alternatively, any of the substrate variations described with referenceto FIG. 4A, supra, may be used. The epitaxial silicon layer is dopedwith a lower concentration of a dopant of the same type as the substrate500. A polysilicon layer 503, is then formed by, for example, chemicalvapor deposition (CVD). In a specific exemplary embodiment, thedielectric layer 501 is silicon dioxide, formed by, for example, thermaloxidation.

In FIG. 5B, a second dielectric layer 504 is formed over the polysiliconlayer 503. In a specific exemplary embodiment, the second dielectriclayer 504 is silicon dioxide and is formed by, for example, CVD.

With reference to FIG. 5C, a photoresist mask 505, with patternedapertures exposing a source region aperture 507, and a drain regionaperture 509 in the second dielectric layer 504 is formed over thepolysilicon layer 503. Both a plan view and cross section are shown.

With reference to FIG. 5D, the second dielectric layer 504 has beenetched to reveal a source window 511, and a drain window 513; the sourcewindow 511 and drain window 513 being aligned along a (100) plane so asto result in current flow along the (100) plane. The photoresist mask505 has been removed. In a specific exemplary embodiment, the seconddielectric layer 504 is etched using hydrofluoric acid, which attackssilicon dioxide rapidly with respect to the photoresist layer 504 andthe polysilicon layer 503. In a subsequent step, the source and drainwindows 511, 513, are further doped with an n-type dopant, for example,phosphorous, creating a source region 515, and a drain region 517. In aspecific exemplary embodiment, the doping is achieved byion-implantation, although alternative means of doping, such asdiffusion, can be used. As is known to a skilled artisan, concentrationlevels will vary dependent on device type. The second dielectric layer504 is used to mask the area which is doped.

With reference to FIG. 5E, a third dielectric layer 519, is formed overthe second dielectric layer 504 by, for example, physical vapordeposition (PVD). While some of the dopant will diffuse into theepitaxial semiconductor layer 503 and the third dielectric layer 519,the concentration of dopant will remain much higher in the implantedregion with respect to the epitaxial semiconductor layer 503.

With reference to FIG. 5F, the central portion of the third dielectriclayer 519 has been etched to a level coplanar with the surface of thesource and drain regions 515, 517. The etched area defines a gate region(discussed below).

With reference to FIG. 5G, a gate dielectric 520, is formed over thegate region. In an exemplary embodiment, a thin oxide layer is formedby, for example, thermal oxidization. In a subsequent step, contactholes 521, 523, are formed using a photoresist to define the area to beetched, then etching the oxide layer 519 by, for example, hydrofluoricacid. FIG. 5G includes a top view as well.

With reference to FIG. 5H, a metallization layer 525, is conformallyformed by, for example, ion beam deposition. In a specific embodiment,the metallization layer 525 is aluminum.

With reference to FIG. 5I, a photoresist layer (not shown) is applied tothe metallization layer 525 and is patterned to result in electricalseparation of a source contact 527, a drain contact 529, and a gatecontact 531. The metallization layer is etched by, for example, ion beammilling. A top view is included.

By fabricating the device with the source and drain aligned with the(100) plane so that source-drain channel current flows along the (100)plane, fabrication induced crystal defects and resultant leakage andparasitic device currents can be reduced.

Another exemplary embodiment utilizing the present invention is a FinFETdevice with source-drain current that flows along a (100) plane. In aspecific embodiment, a silicon substrate with a commercially availableepitaxial silicon layer grown on the surface is used. While the (100)plane is referred to throughout, a skilled artisan will recognize manyequivalent planes that will result in an advantageous intersect anglewith {110}, and {111} planes.

With reference to FIG. 6A, a silicon portion 601A of asilicon-on-insulator (SOI) substrate has a thin silicon dioxide layer603A, a thicker silicon nitride layer 605A, and a patterned photoresistmask layer 607. In a specific exemplary embodiment, the substrate is asilicon-on-insulator wafer. However, a skilled artisan will recognizethat other semiconductor materials may be used instead of an SOI waferfor the substrate. Other semiconductor materials include, for example,elemental semiconductors such as germanium, compound semiconductors suchas group III-V, and II-VI materials, and semiconducting alloys (e.g.,Al_(x)Ga_(1-x)As, HG_(1-x)CD_(x)Te). If elemental semiconductors otherthan silicon, or compound semiconductors are employed, an atomic layerdeposition (ALD) process may be employed for producing thin, highquality oxide layers.

The silicon dioxide layer 603A is a pad oxide to preventthermally-induced stresses from developing between particular dissimilarmaterials, such as between silicon and the silicon nitride layer 605A.The silicon dioxide layer 603A may be thermally grown or deposited. Thesilicon nitride layer 605A is then formed over the silicon dioxide layer603A by, for example, chemical vapor deposition (CVD). In a specificexemplary embodiment, the silicon dioxide layer 605A is between 50 Å and200 Å while the silicon nitride layer 605A is between 400 Å and 2000 Å.The patterned photoresist mask layer 607 may be repeated a number oftimes and disposed laterally over a surface of the substrate 601A tofabricate multiple surrounded-gate devices. For clarity, only one suchdevice will be shown and described herein.

FIG. 6B indicates a fin area 602 being fabricated from the siliconportion of an SOI wafer, exposing an insulating portion 601B. To formthe fin area 602, the photoresist mask layer 607 defines an area forwhich underlying areas will not be etched. These layers (i.e., thesilicon nitride layer 605A and silicon dioxide layer 603A) are etched inaccordance with methods well-known in the semiconductor arts. Forexample, depending upon a chemical composition of a given layer, etchingmay be accomplished through various wet etch (e.g., in hydrofluoricacid, such as contained in a standard buffered oxide etch, ororthophosphoric acid) or dry-etch techniques (e.g., reactive-ion etch(RIE)). Once an etched silicon nitride layer 605B and an etched silicondioxide layer 603B are formed, the underlying substrate 601A is etched,defining the etched substrate 601B. If the substrate 601A is comprisedof silicon, silicon may be wet-etched, for example, with potassiumhydroxide (KOH) or tetra-methyl ammonium hydroxide (TMAH). Dry-etchtechniques, such as a reactive ion etch (RIE) with a fluorine richplasma (e.g., SF₆) are also known in the art for etching silicon. Thefin is aligned along the (100) plane so that source-drain current willflow along the (100) plane.

A sidewall slope of the fin area 602 may be controlled through a choiceof the chemistry used in a dry-etch recipe and/or through a choice ofthe substrate 601A if a monocrystalline semiconductor is used. If asilicon wafer is chosen for the substrate 601A, a dry-etch process maybe chosen to etch approximately 90° sidewalls on the fin area 602.Therefore, the fin area 602 can be fabricated in such a way so as tomaximize a given surface area to volume ratio of the fin 602 therebyallowing electrical characteristics (e.g., carrier mobility) of the FETdevice to be modified and tuned.

After producing the fin area 602, the photoresist mask layer 607 isremoved (FIG. 6C) and a gate oxide layer 609 is thermally grown (FIG.6D) after an appropriate pre-oxidation clean. In other exemplaryembodiments, the gate oxide layer may be conformally deposited by CVD.Thinner layers of gate oxide (e.g., 20 Å to 30 Å) may be deposited bytechniques such as atomic layer deposition (ALD).

In FIG. 6E, a dielectric fill layer 611A is deposited over the gateoxide layer 609. The dielectric fill process may be similar toshallow-trench isolation (STI) type fills known in the art, for example,a high density plasma (HDP) oxide fill. The dielectric fill layer 611Amay be comprised of any insulative material such as silicon dioxide,sapphire, borophosphosilicate glass (BPSG), or any of a number of othermaterials deposited or otherwise formed over the gate oxide layer 609.The dielectric fill layer 611A may also be comprised of oxynitride or ahigh-k dielectric material. However, if oxynitride is used for thedielectric fill layer 611A, then an additional masking step will be usedto prevent the etched oxynitride layer 605B from being etched away insubsequent process steps. The dielectric fill layer 611A may be broughtto a level roughly coplanar with an uppermost part of the etched siliconnitride layer 605B through, for example, chemical mechanicalplanarization (CMP).

The dielectric fill layer 611A is then etched, producing an etcheddielectric fill layer 611B (FIG. 6F). A high-selectivity etchantprevents the etched silicon nitride layer 605B from being substantiallyetched away during the dielectric fill layer 611A etch. Further, if thegate oxide layer 609 is comprised of thermally grown silicon dioxide,the gate oxide layer 609 will etch more slowly than an HDP layer usedfor the dielectric fill layer 611A (i.e., an etch rate of thermal oxideis lower than HDP oxide as HDP is less dense). If an exposed portion ofthe gate oxide layer 609 (i.e., the portion above the etched dielectricfill layer 611B) is not etched completely, it will be removed prior to afinal gate oxidation step described infra.

With reference to FIG. 6G, the etched silicon nitride layer 605B, theetched silicon dioxide layer 603B, and exposed portions of the gateoxide layer 609 are substantially etched away using techniques known toa skilled artisan. An exposed section of the fin area 602 defines anactive region of the FET device. The active region has a given height,H, length, L₁, and width, W. In a specific exemplary embodiment, theactive region height, H, is approximately 100 nm to 450 nm. The width ofthe active region, W, is approximately 100 nm or less and the length,L₁, is dependent on a number of factors such as device design rules andgate widths.

A thermal oxidation, ALD, or high-k oxide deposition process forms afinal thin gate oxide 613A (FIG. 6H) over the active region. In aspecific exemplary embodiment, the final thin gate oxide is grown ordeposited to a thickness of approximately 20 Å to 30 Å. A polysiliconlayer 615A is then conformally deposited (FIG. 6H). The polysiliconlayer 615A will form a gate region, described infra. A patterned secondphotoresist layer 617 is formed and patterned to define the gate; thegate having a width commensurate with a length, L₂, of the patternedsecond photoresist layer 617. FIG. 6I is a plan view of the FET deviceand thus provides clarity in understanding a layout of the device afterthe second photoresist layer 617 is added. The hidden section is anuppermost portion of the channel active region of FIG. 6G.

With reference to FIG. 6J, a selective etch process (either wet-etch ordry-etch) is used to fully define a gate region 615B of the device.Generally, a high selectivity to either silicon or silicon dioxide isaccomplished using CHF₃/O₂, CH₂F₂, or CH₃F chemistry. Doped areas areadded (e.g., by diffusion or implantation) to define a drain contactregion 619 and a source contact region 621 of the device. The patternedsecond photoresist layer 617 is then removed. FIG. 6K provides a planview—showing source, gate, and drain contact areas—of a completed FinFETdevice fabricated according to exemplary embodiments descried herein.

In the foregoing specification, the present invention has been describedwith reference to specific embodiments thereof. It will, however, beevident to a skilled artisan that various modifications and changes canbe made thereto without departing from the broader spirit and scope ofthe invention as set forth in the appended claims. For example, skilledartisans will appreciate that other types of semiconducting (e.g., anycrystalline semiconducting material) and insulating materials other thanthose listed may be employed. Additional particular process fabricationand deposition techniques, such as low pressure chemical vapordeposition (LPCVD), ultra-high vacuum CVD (UHCVD), and low pressuretetra-ethoxysilane (LPTEOS) may be readily employed for various layersand still be within the scope of the present invention. Although theexemplary embodiments are described in terms of MOS integrated circuitdevices, a person of ordinary skill in the art will recognize that otherfabrication techniques, such as bipolar or BiCMOS techniques, mayreadily be employed as well.

While fabrication methods aligning primary device current with the (100)plane is referred to with respect to the exemplary embodiments includedherein, a skilled artisan will recognize the use of many equivalentplanes that will result in an advantageous intersect angle with {110},and {111} planes without departing from the scope of the presentinvention. Additionally, concepts and techniques discussed herein may beadded to various electronic devices as a mechanism by which leakagecurrent is reduced. The specification and drawings are, accordingly, tobe regarded in an illustrative rather than a restrictive sense.

1. A method of fabricating an integrated circuit (IC) device, the methodcomprising: providing a substrate having at least an uppermost portioncomprised of a crystalline semiconducting material; forming a sourceregion on the uppermost portion of the substrate, the source regionbeing doped with a first dopant having a first type of majority carrier;forming a drain region, the drain region being doped with a seconddopant supporting a same-type majority carrier as the first dopant, thedrain region being aligned with the source region such that anysource-drain current flows substantially parallel to a {100} plane ofthe crystalline semiconducting material portion of the substrate, thedrain region being coupled to the source region by a channel regionwithin the uppermost portion of the substrate; and forming a gateregion, the gate region having a third dopant, the third dopantsupporting a majority carrier of opposite polarity to that of the firstdopant, the gate region overlying the channel region, the gate regionfurther being coupled to the channel region by a dielectric layer. 2.The method of claim 1 wherein the substrate is selected to be anelemental semiconductor.
 3. The method of claim 2 wherein the elementalsemiconductor is selected to be silicon.
 4. The method of claim 1wherein the substrate is selected to be a compound semiconductor.
 5. Themethod of claim 1 wherein the substrate is selected to besilicon-on-insulator (SOI).
 6. The method of claim 1 wherein thesubstrate is selected to be oxygen-implanted silicon (SIMOX).
 7. Themethod of claim 1 wherein the crystalline semiconducting material isselected to be comprised substantially of silicon.
 8. An integratedcircuit (IC) device comprising: a substrate having at least an uppermostportion comprised of a crystalline semiconducting material; a sourceregion on the uppermost portion of the substrate having a first dopedregion, the first doped region supporting a first type of majoritycarrier; a drain region having a second doped region, the second dopedregion supporting the first type of majority carrier, the drain regionbeing aligned with the source region such that any source-drain currentflows substantially parallel to a {100} plane of the crystallinematerial portion of the substrate; and a gate region, the gate regionbeing coupled to the channel region by a dielectric layer.
 9. The ICdevice of claim 8 wherein the substrate is an elemental semiconductor.10. The IC device of claim 9 wherein the elemental semiconductor issilicon.
 11. The IC device of claim 8 wherein the substrate is acompound semiconductor.
 12. The IC device of claim 8 wherein thesubstrate is silicon-on-insulator (SOI).
 13. The IC device of claim 8wherein the substrate is oxygen-implanted silicon (SIMOX).
 14. The ICdevice of claim 8 wherein the crystalline semiconducting material iscomprised substantially of silicon.
 15. A method for forming anintegrated circuit (IC) device, the method comprising: providing asubstrate having at least an uppermost portion comprised of acrystalline semiconducting material; forming a fin on the uppermostportion of the substrate, the fin having a given width and length, thefin arranged such that the length of the fin is aligned substantiallyparallel to a {100} plane of the crystalline semiconducting materialportion of the substrate; forming a dielectric layer over the fin;forming a gate region over the dielectric layer, the gate regioncovering a channel, the channel being doped with a material to support afirst type of majority carrier; and doping portions of the fin notcovered by the gate region, the dopant supporting a second type ofmajority carrier.
 16. The method of claim 15 wherein the substrate isselected to be an elemental semiconductor.
 17. The method of claim 16wherein the elemental semiconductor is selected to be silicon.
 18. Themethod of claim 15 wherein the substrate is selected to be a compoundsemiconductor.
 19. The method of claim 15 wherein the substrate isselected to be silicon-on-insulator (SOI).
 20. The method of claim 15wherein the substrate is selected to be oxygen-implanted silicon(SIMOX).
 21. The method of claim 15 wherein the crystallinesemiconductor material is selected to be comprised substantially ofsilicon.
 22. An integrated circuit (IC) device, comprising: a substratehaving at least an uppermost portion comprised of a crystallinesemiconducting material; a fin, the fin having a given width and length,the fin arranged such that a current path of the fin is substantiallyparallel to a {100} plane of the crystalline semiconducting material,the fin further comprising: a source region, the source region beingdoped with a first dopant which supports a first type of majoritycarrier; a drain region, the drain region being doped with a seconddopant which supports the first type of majority carrier; and a channelregion, the channel region being interposed between the source regionand the drain region; and a gate region, the gate region being formed onat least three sides of the channel region, the gate region beingseparated from the channel region by a thin dielectric layer, the gateregion being doped with a dopant which supports a second type ofmajority carrier.
 23. The IC device of claim 22 wherein the substrate issilicon-on-insulator (SOI).
 24. The IC device of claim 22 wherein thesubstrate is oxygen-implanted silicon (SIMOX).
 25. The IC device ofclaim 22 wherein the crystalline semiconducting material is comprisedsubstantially of silicon.
 26. A method of fabricating an integratedcircuit (IC) device, the method comprising: providing a substrate havingat least an uppermost portion comprised of a crystalline semiconductingmaterial; providing an area for forming a source region on a firstsurface of the uppermost portion of the substrate; providing an area forforming a drain region in proximity to the source region area, the drainregion area being aligned with the source region area such that anysource-drain current generated flows substantially parallel to a {100}plane of the crystalline semiconducting material portion of thesubstrate, the drain region being coupled to the source region by achannel region area within the first surface of the uppermost portion ofthe substrate; and providing an area for forming a gate region, the gateregion area overlying the channel region, the gate region area beingcoupled to the channel region by a dielectric layer.
 27. The method ofclaim 26 further comprising forming shallow trench isolation features onthe first surface of the semiconducting material.
 28. The method ofclaim 27 wherein the shallow trench isolation features are formed by:etching a trench into the uppermost portion of the crystallinesemiconducting material; and filling the trench with a dielectric fillmaterial.
 29. The method of claim 27 further comprising locating theshallow trench isolation feature between active areas located on thefirst surface of the uppermost portion of the substrate.
 30. The methodof claim 26 wherein the substrate is selected to be an elementalsemiconductor.
 31. The method of claim 30 wherein the elementalsemiconductor is selected to be silicon.
 32. The method of claim 26wherein the substrate is selected to be silicon-on-insulator (SOI). 33.A method of fabricating an integrated circuit (IC) device, the methodcomprising: providing a substrate having at least an uppermost portioncomprised of a crystalline semiconducting material; providing an areafor forming a source region on a first surface of the uppermost portionof the substrate; providing an area for forming a drain region inproximity to the source region area; and locating the source area andthe drain area with respect to each other such that a line drawn betweenthem is substantially orthogonal to a [100] direction of the crystallinesemiconducting material.
 34. The method of claim 33 wherein the step oflocating the source area and the drain area further includes aligningthe drain region area with the source region area such that anysource-drain current generated flows substantially parallel to a {100}plane of the crystalline semiconducting material portion of thesubstrate.
 35. The method of claim 34 further comprising: coupling thedrain region to the source region by forming a channel region within thefirst surface of the uppermost portion of the substrate; and providingan area for forming a gate region, the gate region overlying the channelregion, the gate region area being coupled to the channel region byforming a dielectric layer.
 36. The method of claim 33 furthercomprising forming shallow trench isolation features on the firstsurface of the semiconducting material.
 37. The method of claim 36wherein the shallow trench isolation features are formed by: etching atrench into the uppermost portion of the crystalline semiconductingmaterial; and filling the trench with a dielectric fill material. 38.The method of claim 36 further comprising locating the shallow trenchisolation feature between active areas located on the first surface ofthe uppermost portion of the substrate.
 39. An integrated circuit (IC)device comprising: a substrate having at least an uppermost portioncomprised of a crystalline semiconducting material; a source region onthe uppermost portion of the substrate; and a drain region located inproximity to the source region and aligned with the source region suchthat a line drawn between the source region and the drain region issubstantially orthogonal to a [100] direction of the crystallinesemiconducting material.
 40. The integrated circuit (IC) device of claim39, further comprising a channel region interposed between the sourceregion and the drain region, the channel region being aligned that anysource-drain current flowing through the channel region flowssubstantially parallel to a {100} plane of the crystalline materialportion of the substrate.
 41. The integrated circuit (IC) device ofclaim 39 further comprising a gate region coupled to the channel regionby a dielectric layer.
 42. The integrated circuit (IC) device of claim39 wherein the substrate is an elemental semiconductor.
 43. Theintegrated circuit (IC) device of claim 42 wherein the elementalsemiconductor is silicon.
 44. The integrated circuit (IC) device ofclaim 39 wherein the substrate is a compound semiconductor.
 45. The ICintegrated circuit (IC) device of claim 39 wherein the substrate issilicon-on-insulator (SOI).
 46. The IC integrated circuit (IC) device ofclaim 39 wherein the substrate is oxygen-implanted silicon (SIMOX). 47.The integrated circuit (IC) device of claim 39 wherein the crystallinesemiconducting material is comprised substantially of silicon.
 48. Anintegrated circuit (IC) device, comprising: a substrate having at leastan uppermost portion comprised of a crystalline semiconducting material;a fin, the fin having a given width and length with rounded uppermostedges, the fin arranged such that a current path of the fin issubstantially parallel to a {100} plane of the crystallinesemiconducting material, the fin further comprising: a source region, adrain region, and a channel region, the channel region being interposedbetween the source region and the drain region; and a gate region, thegate region being formed on at least three sides of the channel region,the gate region being separated from the channel region by a thindielectric layer.
 49. The integrated circuit (IC) device of claim 48wherein the substrate is silicon-on-insulator (SOI).
 50. The integratedcircuit (IC) device of claim 48 wherein the substrate isoxygen-implanted silicon (SIMOX).
 51. The IC device of claim 48 whereinthe crystalline semiconducting material is comprised substantially ofsilicon.